The subject matter of this disclosure relates to a seal assembly for a piston rod, for example for use in a reciprocating compressor which are normally affected by problems of leaking of the process fluid. Such seal assembly can therefore used to prevent leaks of process fluid which is toxic or harmful to the environment.
Conventional piston rods are normally equipped with sealing assemblies defining a chamber, said sealing assemblies having a process surface, exposed to the process fluid, and an internal surface, which is in contact with the barrier fluid inside said chamber.
As shown by document WO2013182456A1 a sealing assembly can be provided with a return line for a barrier fluid. The return line is connected to an inlet and an outlet of the assembly. A pump is placed onto the return line in order to recirculate the barrier fluid from the outlet back to the inlet.
In some instances, a drawback of the type of seal assembly disclosed in WO2013182456A1, wherein the barrier fluid pressure is predetermined and fixed, is that some barrier fluid may flow into the process fluid, especially during the suction phase of the piston, thus increasing the oil consumption of the compressor and potentially increasing the contamination of the process fluid.
Also, regardless of the process pressure, this design inherently requires a recirculation circuit for the process fluid leaking through the pressure breakers. Furthermore, the barrier fluid leakage towards the process is not recoverable.